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Abstract

The Near Surface Mounted (NSM) strengthening is an emerging retrofitting technique, which involves bonding Fibre Reinforced Polymer (FRP) reinforcement into grooves cut along the surface of a concrete member to be strengthened. This technique offers many advantages over external bonding of FRP reinforcement, for example, an increased bond capacity, protection from external damage and the possibility of anchoring into adjacent concrete members. To date, significant research has been conducted into the NSM FRP strengthening technique. However, there are still some areas which need further research in order to fully characterise bond and anchorage of NSM FRP bars. Lack of experimental data, design tools and analytical models addressing these areas create obstacles for the efficient use of these advanced polymer materials. The particular objectives of the research are; to investigate bond behaviour between NSM FRP bars and concrete, to understand the critical failure modes involved and their mechanics, and to develop a rational analytical model to predict bond strength and anchorage length requirements for NSM FRP bars. Several significant variables affecting bond, such as bond length, size, shape and type of bar, resin type, groove dimensions and concrete strength, have been considered. In particular, attention has been focussed on the effect of bar shape on bond behaviour. A comprehensive set of laboratory testing and their results, including the effect of the investigated parameters are presented. Various modes of anchorage failure of NSM FRP bars are identified and the underlying mechanics are investigated. Analytical models are developed to predict bond capacity and anchorage length requirements of NSM FRP bars, and are verified with experimental results.

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